1. Field of the Invention
The present invention relates to a method for forming a waterproof joint section of a wire harness to be arranged in an automotive vehicle or the like and a wire harness including a waterproof joint section formed by such a method and is particularly designed to treat joined sections at ends of a plurality of wires without using a waterproofing agent.
2. Description of the Related Art
As a method for joining and connecting a plurality of wires constituting a wire harness at their ends, there are a method using a joint connector and a method for forming a terminal joint section by joining exposed core sections at the ends of the wires by welding, fusing or another means. In either case, this joint section needs to be waterproofed in the case of being arranged in a water susceptible area such as an engine compartment.
FIG. 10 shows an example of connection using a joint connector disclosed in Japanese Unexamined Patent Publication No. H05-3057. A joint connector 1 includes a housing 1a provided with a shorting terminal (not shown) by insert molding. After a female terminal 2 connected with an end of a wire w is inserted into the housing 1a and connected with the shorting terminal, a cover 1c is fitted into an opening 1b of the housing 1a and a waterproof plug 3 is mounted at a connected part of the wire w and the female terminal 2 to prevent water penetration into the housing 1a. 
However, the joint connector of this type requires the housing 1a formed by molding, is difficult to miniaturize and, in addition, requires a part such as a terminal or a busbar, which increases cost and makes it difficult to deal with a design change. Further, for a waterproof treatment, it is necessary not only to mount the cover 1c onto the housing 1a to prevent direct water penetration, but also to mount the waterproof rubber plug 3 on each wire w to prevent water penetration through clearances inside an insulating coating of the wire w by a capillary action.
On the other hand, FIG. 11 shows an example of connection by forming a terminal joint section disclosed in Japanese Unexamined Patent Publication No. 2005-228603. Insulating coatings 4a at end portions of a plurality of wires 4 are peeled off to expose cores 4b, and a conductive sleeve 5 is crimped and connected to the exposed sections of the cores 4b to form a joint section 6. This joint section 6 is inserted into a bottomed connection cap 7 through an opening 7a, a sealant 8 is injected through a hole 7d formed in a bottom wall 7c of the connection cap 7 to be infiltrated around the joint section and also between the cores 4b and the like by a capillary action with the joint section 6 temporarily fixed by flexible locking arms 7b projecting in the connection cap 7, and then the sealant 8 is hardened. In this way, a waterproof treatment is applied. If the sealant 8 has a high fluidity, it is also possible to inject the sealant through the opening 7a of the connection cap 7.
If the terminal joint section 6 is formed and connected as described above, a housing is not necessary unlike the case of using a joint connector. Thus, miniaturization is possible and a part such as a terminal or a busbar is not necessary, wherefore cost can be reduced and a design change can be easily dealt with.
However, since the liquid sealant 8 is used by being filled into the connection cap 7 for the waterproof treatment, a specified time is required to harden this sealant 8, thereby extending an operation time and, in addition, a space is unnecessary to hold the connection cap 7 in a stable state where no external force acts until the sealant 8 is hardened. Particularly, in order to infiltrate the sealant 8 into the clearances between the cores 4b of the wires 4 and clearances between the cores and the connection cap to fill up these clearances, the sealant 8 needs to have a low viscosity and, in this case, a hardening time becomes even longer, thereby causing a problem that the waterproof treatment cannot be quickly performed.
In view of the above problems, an object of the present invention is to provide a waterproof joint section forming method capable of reducing the number of parts in a waterproofing process, reducing cost for a waterproof treatment, for example, by shortening a waterproof treatment time and easily and reliably performing the waterproof treatment, and a wire harness provided with a waterproof joint section formed by such a method.